1. Field of the Invention
The present invention generally relates to a clamping tool apparatus for stacking a plurality of Nd—Fe—B permanent magnets and a method for bonding a plurality of Nd—Fe—B permanent magnets.
2. Description of the Prior Art
Recently, with the increasing use of Nd—Fe—B permanent magnets in motors, rotor eddy-current loss has become a key factor that affects the reliability of high speed permanent magnet motors' operation. Because the rotors have poor heat dissipation, eddy-currents generated by the permanent magnets spun at a high speed will increase the rotor's temperature thereby causes the permanent magnets to demagnetize. Therefore, a plurality of Nd—Fe—B permanent magnets are bonded together to reduce the rotor eddy-current loss.
Traditional methods of bonding the Nd—Fe—B permanent magnets include using glass beads mixed together with adhesives. Then, the glass beads and the adhesives are applied to the surface of the Nd—Fe—B permanent magnets. A clamping tool apparatus is used to sandwich the Nd—Fe—B permanent magnets together. Then, the Nd—Fe—B permanent magnets are cured. However, there are many drawbacks associated with the traditional method. Specifically, mixing the glass beads reduces the strength of the adhesive. In addition, the glass beads are not all uniform in size; therefore, it is difficult to have a layer of adhesives between the permanent magnet that has uniform thickness. Furthermore, the use of glass beads creates a large gap between the Nd—Fe—B permanent magnets. When sandwiching the Nd—Fe—B permanent magnets, some of the glass beads may move or be crushed, this makes it difficult to maintain the insulation characteristics between the Nd—Fe—B permanent magnets. Therefore, the success rate of using the traditional method to bond the Nd—Fe—B permanent magnets is very low and, often, additional tests are required to ensure proper insulation exists between the Nd—Fe—B permanent magnets.
Such a clamping tool apparatus is disclosed in Chinese Patent 101763929 B. The clamping tool apparatus includes a frame having a U-shape in cross-section. The frame includes a lower plate and a pair of magnet positioning members. The magnet positioning members are disposed on the lower plate spaced from one another and extending perpendicularly outwardly from the lower plate to define the U-shape and a chamber between the lower plate and the magnet positioning members. An upper plate extends between the magnet positioning members and slidably attached to the magnet positioning members. A fastener is slidably dispose on each of the magnet positioning members to secure the upper plate between the fastener and the lower plate.
Such a method is also disclosed in the Chinese Patent 101763929 B. The method includes a method for bonding a plurality of Nd—Fe—B permanent magnets having a first Nd—Fe—B permanent magnet and a second Nd—Fe—B permanent magnet. The plurality of Nd—Fe—B permanent magnets also includes rust and grease disposed on the surface of the Nd—Fe—B permanent magnets. The method uses an insulating adhesive and the clamping tool apparatus. The clamping tool apparatus includes the lower plate having the pair of magnet positioning members extending outwardly from the lower plate. The upper plate is slidably disposed on magnet positioning members. The fastener is disposed on each of the magnet positioning members.
The method includes a first step of cleaning the plurality of the Nd—Fe—B permanent magnets including the grease and the rust to remove the grease and the rust. The next step of the method is depositing a layer of insulating adhesive on the surface of each of the Nd—Fe—B permanent magnets. Then, the layer of insulating adhesive on the surface of second Nd—Fe—B permanent magnet and the layer of insulating adhesive on the surface of the first Nd—Fe—B permanent magnet are sandwiched between the first Nd—Fe—B permanent magnet and the second Nd—Fe—B permanent magnet by stacking the second Nd—Fe—B permanent magnet on the first Nd—Fe—B permanent magnet to combine the layer of insulating adhesive on the surface of second Nd—Fe—B permanent magnet and the layer of insulating adhesive on the surface of the first Nd—Fe—B permanent magnet to form a combined adhesive layer of insulating adhesive between the first Nd—Fe—B permanent magnet and the second Nd—Fe—B permanent magnet. Next, a predetermined clamping pressure is applied to the first Nd—Fe—B permanent magnet and the second Nd—Fe—B permanent magnet to produce a stacked Nd—Fe—B permanent magnet. The next step of the method is curing the stacked Nd—Fe—B permanent magnet. After curing the stacked Nd—Fe—B permanent magnet, the stacked Nd—Fe—B permanent magnet is cooled to room temperature. Then, the stacked Nd—Fe—B permanent magnet is machined. After machining the stacked Nd—Fe—B permanent magnet, a protective layer is deposited on the stacked Nd—Fe—B permanent magnet.